AJH Synth MiniMod VCA - Manual (Page 3)

6 CV Input 2 : Works in the same fashion as CV Input 1. Any voltage applied to this Input is attenuated
by CV 2 Level control (8) and summed with CV 1 Level output voltage, the resultant
control voltage regulates the gain of VCA 1 between zero and unity.
Note that CV 1 & CV2 act on VCA 1 ONLY, see signal flow diagram below.
7 CV Level 1: Sets the amount of control voltage (between 0% and 100%) sent from CV Input 1 (5) to
regulate the gain of VCA 1
8 CV Level 2 : Sets the amount of control voltage (between 0% and 100%) sent from CV Input 2 (6) to
regulate the gain of VCA 1
9 VCA 1 Offset :
Sets the initial gain of VCA 1 by applying a control voltage directly to the CV input node,
so that it effectively acts as a manual volume control for the VCA . See the signal flow
chart below for a visual indication of function.
12 Audio Output : Audio output. The output signal level is typically +/- 5V but can be much higher (up to
+/-11v) if the Gain Jumper (J1) is removed, so it is important that the output level is
controlled with the Master Level Control (10) to prevent overloading modules which are
connected downstream.
Removing this Jumper boosts the level of signal fed to the input of VCA 1 by almost
300%. This overdrives the VCA core and creates up to 20% of tube-like harmonic distor-
tion. With the Gain Jumper removed care must be taken to adjust the Master Level
control to reduce the gain of VCA 2 by a corresponding amount and keep the output
level around +/-5V to prevent possible damage to other modules downstream of this
module.
10 Master CV Input : A voltage applied to this input varies the gain of VCA 2. When no jack is connected the
switch contact of the jack socket is connected (normalised) to +10V and the gain of the
VCA can be manually controlled by the Master Level control (10). This emulates the
“Pedal” control and Input of the Model D, but with a greater gain range. Control voltages
up to +10V can be connected to this Input.
11 Master Level : Controls the CV voltage level to VCA 2. If no jack is connected to Master CV Input (9) then
a setting of 5 (12 o’clock) will give unity gain for VCA 2. If VCA 1 is being over driven by
removing J1 (C) then this can be turned down so that unity gain from the VCA Output is
maintained, in a similar fashion to the Master volume control on a guitar amplifier.
If a CV signal is fed into Master CV Input (9) then this controls the level of this signal fed to
the VCA gain cell between 0% (no audio output) and 100% (Unity gain with +/-5V audio
input).
VCA 2 VCA 1
Audio Input 1
Audio Output
CV IN. 1
CV
Level
1
CV
Level
2
CV IN. 2
Audio Level 1
MiniMod Cascaded VCA
Gain Jumper
Master Input Jack
Normalled to
+10V Internally
Master CV Input
+10V
+5V
Master
Level
Audio Level 2
CV Offset
Audio Input 2
Audio and CV Signal Flow Chart
C Gain Jumper :
(J1 on PCB)